Hydraulic brake



I A N Feb. 13, 1945. i 0, RAISMUSSEN 2,369,313

HYDRAULIC BRAKE Filed April 13, 1942 2 Sheets-Sheet l Qttornegs Feb. 13, 1945. v o, RASMUSSEN 2,369,313

HYDRAULIC BRAKE 3x1-mentor UNITEDSTAT Patented Feb. 13, 1945 Olaf Rasmussen, Dayton, Ohio, assignor to General Motors Corporation poration of Delaware Detroit, Mchwa cor- `Applicatie"ni Aprilia, `194,2, serial No. 438,761

iolaims. (o1. en -54.5)

This invention relates "to hydraulic applying mechanism `and-hasbeen designed particularly for vehicle brakes. In particular it relatesrto an applying mechanism Awhich includes two inde-f pendent systems,` one for one brake on set-of brakes and the other for ,another` brake or set of brakes, together with means to effect pressure equalization between said systems. .I l A Anobjectgof the invention-,is to provide such a mechanism with an auxiliary cylinderhaving aiioating piston which shall move in response to` unbalanced fluid pressure in thetwo end spaces of` said cylinder `which spaces constitute parts of i the twosystems. t

A `further object is to provide springsin said auxiliary cylinder which springs shall resist the movement of the floating piston `under the influence; of unbalanced fiuidpressure `but which shall not. supplement `said unbalanced pressure," Other objects and advantages will beunderstood from` the description whichfollows:

On the drawings: Figure 1 is;a View in elevation u Figure 2 `is a horizontal section through the` two mastercylinders. y

Figure 3 is a detail showing the operating means. i

Figure 4 is a vertical section through vthe equalizing cylinder on line 4-#4 of Figure 2.

Figure 5 is a similar section through a modied form of equalizing cylinder. l l l Referring to the drawings, there may beseen parallel master cylinders and I3. In each is a piston l5. At Il is a substantially conveneI in plan a part of tional reservoir, there being the usual communieating passages IB and 18a between the reservoir and cylinders.` The two pistons are to be jointly applied by rods l Sconnectedby a suitable crosshead 20 to a pedal 2|. 1 The casting within which the cylinders are formed also contains an` auxiliary equalizing cylinder 23 having `an axis partly in section;

under side" of Ithe dome` oiwhich secured 'a `flexible 'closurev member `45 adapted to prevent return flow of fluid into said spaces through openings Min the stamping. `Ihestamping is biased to a position` engaging fits seal by a spring 49 engaging the ilange 4l andfin abutment with the bottom of a cup 50 located adjacent toor in contact `with the pistonseal "21. Under the influence of thebrake return springs, not shown, the cup Iltis lifted from seal 39 against the' lesser resistance of spring 49 and, uid'flows intothe cylinder end space from the conduit `until the fluid pressure equals the opposingspring pressuref` In this waythe `desired residual pressure is maintained in the conduit and wheel( cylinders.

The cup 50 is shownto be provided with apertures 5l through which uid may ow to reach thefregion adjacent the valve. `Thecup 50 has l aradial lian ge 53 adapted to engage a shoulder 54 formedon thecylinder'wallr Itfisbiased to such engagement bya spring 55, theoppositeend of which `spring engagesla radial "flange -51 of an `angular stop member 59. Flange 51 seats on the end cap asshown.` The body of stoplniernber 59 is adapted to be contactedby iiange 53 of cup 50 to limit the endwise `movement of said cup ,and of thepiston 25.

In the normal operation, the fluid from the two master cylinders enters the end spaces of the` auxiliary `cylinder and under the influence of pressure originating in the master cylinders passes through the stampings by lifting the iiexible closures 45 and flows towardthe wheel cylinders to apply the brakes. In theevent that pres-` sure builds upin one of theseend spaces more thanin the other because of unequal shoe `c1earances, the unbalanced pressure will move the floating piston to restore thebalance.` Indoing A so, the piston is moved against the resistance of at a right angle to the axes of parallel cylinders Il and i3. Within cylinder 23 is a oating piston 25 having sealing means 2l. From master cylinder I3 a passage 29 leads to a space 30 betweenpiston 25 and the end cap 3| of the aux# ilangelll of a cup shaped stampingj43 to the springs 49 and 55. The movement will nottake `place until the built-up fluid pressure is able to, of itself, overcome the opposing .l force of the springs for the reason that Jthe piston is not held inbalance `between the springs of the two spaces. The springs lfunction to hold the flanges 53 against thesshoulder 54. 'I'hese springs do not l a break occurs inthe conduit to one of the brakes,

. two systems remain eiective.

supplement Vthe unbalanced iluid pressure in moving the piston.` The actionof the piston is `therefore stable. In the event of excessive fluid pressure diierences in the end spaces as where the cup flange 53 is stopped on the member 45 `and the brakes `operated by at least one of the `While the construction above describedmay be referred to as a preferred embodiment, a somewhat modied form is shown in Fig. 5. It differs not in iunctionbut in that it uses but one spring to bias the outlet valve to closed position andl to bias the cup flange'into Contact with the cylinder shoulder. In this form, passages 29' and 33 afford communication with. the master cylinders is engagedfaasi'beforeby xthe valve stampingiS; which carries the closure 45 over openings ll'l.`

lea-ding from said end spaces whereby instrumentalities served thereby may be subject to master cylinder pressure, springs in said end spaces adapted to resist movement of said floating piston in either direction, and stop means whereby said springs may not supplement the unbalanced iiuid A cup 50 replaces cup 50. It is similar, however; e

let 6I in a master cylinder and` that Figurew4l.

shows other outlets .63 from the, end spaces.

These -outlets -arenot' apart off the :inventionu They may be" used,1`as willV be obvious, fora signal` light switehand for 'the' connection yof `conduitstov gagesto indicate differences of'flui'dpressure in. the twosystems;y

-1 claim:

1."Hydraulic 'operating mechanism comprising two independentsystems, eachA system including aconduit containing La variable volume space; movablemeansxinversely'to change the Volume of said 'spaces inre'sponse to unbalanced fluid pressure therein,v springmeans to resist "mover ment of saidinovable means and stop irneans' whereby said spring means' may' not supplement said uid' pressuremeans iny moving said mov"-A able mean's.

` 2. Hydraulicloperating mechanism comprising a pair of master cylinders arranged inparallel relationgjpistons'therein, means to move said pis,- tons jointly; `an auxiliarycylinder, a piston float; ing 'therein' and .forming jend spaces, means affording communication between'V said master 'cyli in'ders` and Vend spaces, outlet means from Vsaid end spaceswoeway check valves controllingsaid outlet means; and other 'and unrestricted outlets pressure in moving said floatingpiston.

3.Inhydraulic-applyingmechanism, al pair of master s cylinders', pistonsr therein; means jointly to move said pistons, an equalizing cylinder, a

piston floating therein and forming end spaces,

passage means between said master cylinders and spaces,--shoulders in said spaces, a member in each,` spaceadaptedto be engaged by the float- (inglpistonandz'having a ange adaptedto engage saidI shoulder toxlimit its inward movement and a v spring operable to bias saidmember into a position whereth'e Vflange contacts the shoulder and thereby; limits the movement of the piston in response to the spring.

4; The invention defined Jby claim 3, together with aJ stop member adjacent they outeri 'end A'of each'ispace, `saidstoprmember constituting anT abutment for-saidspring and, by contact with' saidmember', limiting the outward movement of;-

said member and "floatingpiston.

5.'-The invention -definedby claim 3, each-*said* f member being of V'cup shape, the base-of tliecup` K being normallyIk adjacent Asaid floating piston and itsilange'lbeingfnormallylfinfcontact with 'said' shoulder.

611 The invention defined by` claim- 3, together with two Way'valve means controlling the' outlets from `each space, said valve means havinglaflange fand a second spring Yterminally engaging said flangefand said membert' 7. "Th'einvention dened by claimfBf, said'shoul ders'being formed in thecylinder wall, together-v with two-way-r valve meansl controlling the outlets fromsaidl spaces; each valvev means` having a ange and f secondvsprings positioned Ibetweenl said flanges and the wallsv of thefmembers-remotewfrom the-faces engagedy by f thev floating OLAF`RASMUSSEN. 

